Assessing Cognitive Impairment.

A plethora of tools and methods are being used to evaluate alcohol's effects on cognitive functioning. Neuropsychological tests focus on identifying the brain regions affected by alcohol, whereas neurocognitive approaches attempt to distinguish impaired cognitive processes. These approaches are supplemented by neurophysiological and neuroimaging tools. Studies using all these instruments have characterized alcohol's effects on cognitive functioning after both acute and chronic alcohol consumption. However, there are limitations to the generalizability of these findings because the subjects in the vast majority of studies do not adequately represent all subgroups of the general population.

C hronic alcohol abuse frequently is also are mentioned. The article concludes closely the complex processes involved in accompanied by significant im with a discussion of factors that may limit cognitive functions. pairment in mental abilities the general applicability of current research Many of the tests described in table 1 Knight findings, specifically age and gender biases are capable of detecting rather subtle cogni and Longmore 1994), and even acute alco in the choice of study subjects. tive dysfunction. The relevance of such hol consumption (i.e., a single drinking subtle impairment is unclear. Although episode) temporarily can affect the drinker's detoxified alcoholics typically achieve cognitive functioning. However, the exact NEUROPSYCHOLOGICAL AND significantly lower scores on these tests nature of the cognitive impairment caused NEUROCOGNITIVE ASSESSMENT than do control subjects of equivalent age, by alcohol (i.e., the mechanisms underlying educational level, and socioeconomic impairment) remains confusing and contro Much of the work regarding the effects of status, their level of dysfunction cannot versial. Some of this confusion stems from a chronic alcohol consumption on mental necessarily be considered "clinically im lack of adequate description by researchers processes has focused on identifying spe paired." Some critics have argued that the of how cognitive functioning has been cific neuropsychological domains-and the sensitivity of these tests has been achieved assessed. Such vague descriptions are par brain regions associated with them-that at the cost of relevancy (for a discussion, ticularly apparent in review articles and in are affected by alcohol. These empirically see Nixon 1993). In other words, a subject reports in the popular media. A large num determined functional domains describe who performs poorly on these carefully ber of different tests and methods are used areas of cognitive or psychological func developed laboratory tests may be able to to evaluate cognitive functioning in alcohol tioning, such as abstract thinking and function quite well in the "real" world. In studies. Failure to characterize the approach problemsolving or perceptualmotor skills. response to this concern, new assessment used in the studies limits the interpretation In early studies of alcohol's effects, tools increasingly focus on tasks relevant to and application of current findings.
cognitive test batteries generally evalu reallife situations. As illustrated in table 2, To illustrate how cognitive functions and ated overall intelligence and neuropsycho these tasks assess performance in several cognitive impairment can be assessed, this article reviews some of the methods used to logical functioning. Researchers since cognitive skill areas. evaluate alcohol's impact on cognitive have refined these tests to assess more performance. These methods include neu specific aspects of intelligence or neu SARA JO NIXON, PH.D.,   Halstead-Reitan Battery (HRB; Russell et al. 1970) Seldom administered in its entirety; subtests used to assess specific NP domains (see below).
Seven subtests addressing multiple NP domains, including frontal lobe function and right and left hemisphere function. Provides an "impairment index" as the ratio of failed versus normal tests.
Shipley Institute of Living Scale (Zachary 1986) Provides "mental age" scores for vocabulary and abstracting skills. Allows estimate of overall conceptual quotient (i.e., a combination of vocabulary and abstracting skills) and WAIS-R IQ. Performance on the vocabulary test rarely is affected in chronic alcohol studies and often is used as a control measure.
40-item vocabulary test combined with a 20-item verbal problem-solving test. Both parts have items of varying difficulty.

Learning and Memory: Verbal and Visuospatial
Wechsler Memory Scale (WMS; Wechsler 1945Wechsler , 1987b Selected subtests generally are used for specific research questions (see below). Recent revisions of the scale may increase its use (for discussion, see Knight and Longmore 1994).
Seven subtests assessing general knowledge, mental control, short-term memory, verbal learning, and memory for stories and figural representations.
Russellʼs Version WMS (Russell 1982) Provides immediate and delayed (30 minutes) assessment, thus providing a means to determine memory function. Use of both subscales allows assessment of both left hemisphere (verbal memory) and right hemisphere (figural memory) function.
Uses two subscales of the WMS: memory for stories and memory for figural representations.
Luria Words Test (Verbal) (Luria 1976) Ascertains acquisition patterns of information and differential memory. Uses common concrete nouns, thus reducing confounding issues of familiarity with the words or of abstraction.

Rey Auditory Verbal Learning
Test (RAVLT; for information, see Lezak 1983) Not commonly used in alcohol-related studies.
Lack of a published manual may contribute to this omission.
Measures the acquisition and retention of multiple verbal lists.

Wisconsin Card Sorting Test
Classic test of the ability to shift problem-Subject sorts cards into one of four piles based (WCST; Heaton 1981) solving strategies with minimal feedback. on color, form, or number. Primary DVʼs 1 are Successful subjects respond with a change the number of categories completed, number in sorting strategy when told that a sort is of total errors, and number of perseverative "incorrect." Computer assistance facilitates errors (i.e., failure to change categories). test administration and scoring.   (Russell 1975) more sensitive to alcohol effects. Time to (number 1 to number 13) with a line. Form B: completion is the more frequently reported DV.
Subject connects alternating numbers and letters (1 to A to 2 to B, etc.) with a line. DVʼs are time to completion and number of errors.

WAIS-R Digit Symbol
A subtest of the WAIS frequently used in Subject copies the symbols assigned to digits Substitution Test alcohol studies. Not a true memory test. 1 to 9 below each digit. The symbols always (Wechsler 1987a) are available for reference. DV is the number of symbols correctly substituted in 90 seconds.
Grooved Pegboard Test Time to completion with the nondominant hand Subject places round, grooved pegs in a grooved (Sander et al. 1989) is more sensitive to alcohol effects. pegboard. Task is completed first with the dominant hand, then with the nondominant hand. DV is the time to completion.

Visuospatial, Nonmemory Skills
Little Men Test (Acker and Computerized administration facilitates time A manikin holding a briefcase is shown in one Acker 1982) and accuracy measurements. of four positions (i.e., upright, inverted, facing toward the subject, or facing away from the subject). Subject identifies which hand is holding the briefcase. DVʼs are reaction time and number of errors.
Mazes (Acker and Acker 1982) Part of the same test battery as the Little Men Subject identifies matching but rotated mazes. Test. Computerized administration facilitates DVʼs are reaction time and number of errors. time and accuracy measurement.

WAIS-R Block Design
Part of the WAIS-R test battery. Classic Subject reconstructs designs of red and white (Wechsler 1987a) measure of visuospatial/ perceptual-motor squares with a set of red and white blocks. DVʼs skills.
are time to completion of individual designs, number of designs completed, and number of completion errors.

Other Tests
Verbal Fluency (Thurstone Classic assessment of verbal production. Pro-Subject produces as many words as possible 1938; Newcomb 1969) duction has been studied for both phonetic and beginning with a specific letter (phonetic) or semantic tasks. Data from alcoholics are incon-belonging to a specific category (semantic) sistent. Some studies reveal significant effects; within a certain time. others do not (for review, see Hewett et al. 1991).

Short-Term Memory
Various forms of Sternbergʼs protocol for asses-A series of letters or numbers are presented (Sternberg 1966(Sternberg , 1975 sing short-term memory are common components individually at a rapid rate. An individual letter in neurocognitive test batteries for alcoholics.
or number then is presented and the subject Computerized administration facilitates reaction has to indicate whether it was presented before. time and accuracy measurement.
Subject also has to recall the letters and numbers presented. 1 DV = Dependent variable, the measurement used in the test.

The Neurocognitive Assessment Approach
In recent years, a new approach adopted from the field of neurocognitive science has been applied to studies of chronic alcohol effects. This approach focuses on the specific processes underlying cognitive functioning (e.g., perceiving, learning, and remembering information). Although the specific perform ance requirements are similar for both the neurocognitive and the traditional neuropsy chological tests, the variables being meas ured and analyzed are different. For example, in both approaches, sub jects may be asked to memorize a story, associate pairs of items, or identify a target. The neuropsychological approach might focus on determining whether skills associ ated with right hemisphere function (e.g., visuospatial skills, such as replicating de signs or geometric figures) or with left hemisphere function (e.g., verbal skills, such as identifying meaningful words) are impaired after chronic alcohol abuse. In contrast, the neurocognitive approach might assess alcohol's differential effects on processes such as the perception, encoding (i.e., processing of information in the brain), or retrieval of information.
Because of their different focuses, the two approaches also differ in their clinical significance. For example, the neuropsy chological approach can locate an impaired brain region (e.g., damage to the right or left hemisphere) based on the functional impairment observed. Similarly, neuropsy chological tests can identify brain regions and their associated functional domains that have been spared from damage. The neu rocognitive approach, on the other hand, by identifying underlying cognitive processes or mechanisms, may help develop treat ment strategies attempting to rehabilitate these specific processes.
The increasing interaction of basic neuropsychological research and process oriented neurocognitive research repre sents a new phase in the study of alcohol related cognitive impairment. Some studies incorporate both neuropsychological and neurocognitive techniques. Although this combined approach requires a higher time commitment both for participants and for researchers, it creates an extensive knowl edge base regarding brain/behavior relations that may help improve the understanding and treatment of alcoholinduced cogni tive dysfunction.

NEUROPSYCHOLOGICAL CONSEQUENCES OF CHRONIC ALCOHOL ABUSE
The findings regarding cognitive deficits following chronic alcohol abuse vary con siderably. However, most neuropsychologi cal studies indicate that detoxified alco holics frequently demonstrate longlasting deficits in four domains: abstract thinking and problemsolving skills, verbal skills and/or memory, perceptualmotor skills (e.g., putting pegs in a pegboard or finger dexterity), and visuospatial skills (Glenn et al. 1993;Tivis et al. 1995). (A discus sion of the association of these domains with specific brain regions is outside the scope of this article. For reviews, see Lezak 1983;Kolb and Wishaw 1985; The neuropsychological domains appear to be differentially sensitive to the effects of chronic alcohol consumption. Whereas abstract thinking, perceptual motor skills, and visuospatial skills al most always are affected by chronic alcohol abuse, alcoholrelated deficits in verbal skills appear less frequently (Parsons 1987). The reason for this pat tern is not entirely clear. It could be re lated to the fact that typical verbal tasks often involve overpracticed skills (i.e., skills performed many times in everyday situations), which are relatively impervi ous to decline. This conclusion is sup ported by studies that detect significant deficits in verbal skills after chronic alcohol abuse when difficult verbal tasks are used (Parsons 1987). However, addi tional work is needed to clarify the nature of these verbal deficits.  Nixon and Parsons 1991) tasks, the test appeals to most participants. The to identify and isolate relevant from irrelevant task requires less than 5 minutes to administer. variables.
Adaptive Skills Battery (ASB; Current data suggest that "typical" responses Subject has to produce the "typical" response or Jones and Lanyon 1981; are more sensitive to alcohol effects. Test may the "best possible" response to 30 vignettes Nixon et al. 1992) require 30 to 45 minutes to administer. Stand-involving interpersonal relations. ard scoring protocols are available.

Face-Name Learning (Becker
The multitrial presentation format allows Subject must learn the correct names for indiet al. 1983; Schaeffer and measurement of learning curves as well as of vidual faces. Stimuli are presented at a con -Parsons 1987) final performance levels. stant pace. Multiple sets of tests are performed.

Rivermead Behavioral Memory
Has been applied primarily with Wernicke-11 subtests assess performance on items rele-Test (RBMT; Wilson 1987; Korsakoff patients. vant to successful independent functioning Wilson et al. 1985) (e.g., remembering a short route, hidden object, or appointment).

California Verbal Learning Test
The wide variety of dependent variables (i.e., Uses two different "shopping lists" to assess (CVLT; Delis et al. 1987Delis et al. , 1988 measurements used in the test) makes the test acquisition of verbal information. Dependent appropriate for many alcohol-related questions.
variables are rate of learning, use of strategies, accuracy, interference, order errors, persistence in errors, and confusion between lists.

NEUROPHYSIOLOGY AND NEUROIMAGING
In addition to performancebased neuro psychological and neurocognitive tests, neuroimaging techniques also are used to assess alcoholrelated cognitive impairment. These techniques include electroencephalo graphy (EEG), magnetic resonance imaging (MRI), positron emission tomography (PET), single photon emission tomography (SPECT) and computerized tomography (CT). (For a review of these and other techniques, see Zakhari and Witt 1992.) Although all these techniques can detect neurophysiological changes associ ated with chronic alcohol consumption, EEG's are used most frequently. This is due in part to the technical aspects of data collection and interpretation, the rela tively low cost, and the ready availability of EEG's. In the study of cognitive pro cesses, specific EEG components called eventrelated potentials (ERP's) often are used. ERP's are changes in the brain's electrical activity in response to the pre sentation of discrete stimuli. ERP's con sist of several components ("peaks" and "valleys") that occur at different times after stimulus presentation and that appear to be related to specific aspects of cogni tive functioning. (For additional informa tion on these components and how they are affected by alcohol, see the article by Porjesz and Begleiter, Chronic alcohol consumption is fre quently associated with alterations in the P300 component, a positive component (i.e., peak) of the ERP occurring approxi mately 300 milliseconds after the presen tation of a relevant, but rare, stimulus. In a prototypical experiment called the odd ball paradigm, subjects must attend to a specific infrequent stimulus (e.g., count the number of occurrences) while ignor ing another more frequently occurring stimulus. For example, subjects observing a series of red and green dots appearing in rapid succession on a computer screen, with the green dots outnumbering the red ones, are asked to count the "rare" red dots. The occurrence of the rare yet rele vant red dots among the irrelevant green dots elicits a P300 ERP response.
The P300 has been associated with target identification and the memory updat ing system (i.e., recognizing and remem bering a stimulus) (Coles et al. 1990). Current research generally indicates that alcoholics produce delayed and/or smaller P300 peaks than do control subjects (for a review, see Porjesz and Begleiter 1993).
The implications of this finding have not been fully developed; current data indicate only a modest correlation between neuro physiological aberrations and cognitive performance as measured by behavioral tests, such as those in tables 1 and 2. More research directed at understanding this inconsistency is needed to elucidate the effects of chronic alcohol consumption on the relationship between brain neurophysi ology and behavior.

COGNITIVE EFFECTS OF ACUTE ALCOHOL ADMINISTRATION
Although the types of tasks used to assess acute alcohol effects often are similar to tasks used to assess chronic alcohol ef fects, the primary focus of the two types of studies has been different. Specifically, contrary to the studies of longterm alco hol effects on cognition, studies of acute effects have tended to focus on tasks that assess performance of functions relevant to driving and other practical skills. Thus, many of these studies have used an infor mationprocessing approach with particu lar interest in changes in reaction time and response accuracy under various condi tions of alcohol exposure.
There have been literally thousands of studies conducted on the effects of acute alcohol administration. Several reviews, such as the ones described below, attempt to integrate this vast literature. In addition to summarizing the general findings, these reviews illustrate the broad range of variables and techniques used to assess alcohol's effects on cognitive functioning. Moskowitz and Robinson (1988) reviewed 158 studies conducted between 1940 and 1985, considering nine perform ance measures: reaction time (i.e., re sponding to a specific stimulus), tracking (i.e., following the movement of an object on a computer screen), vigilance (i.e., responding to an infrequent, relevant stimulus against a background of fre quent, irrelevant stimuli), divided atten tion (i.e., performing two tasks at the same time), visual function, information processing, perception, psychomotor skills, and driving. The authors concluded that divided attention tasks provided the most sensitive measure of impairment. Sixty percent of the studies reviewed detected impairment at blood alcohol concentrations (BAC's) at or below 0.05 percent 1 with divided attention tasks. Performance of the other tasks was not impaired to the same extent.
More recently, Holloway (1994) summa rized 148 studies conducted between 1985 and 1993. This review focused on studies ad dressing the effects of a range of low doses of alcohol that are relevant for social drinkers. Instead of focusing only on performance tasks, especially those obviously related to driving and other highrisk behaviors, Holloway also considered the effects of alcohol on subjective measures (e.g., nega tive effects, such as feeling intoxicated, and positive effects, such as feeling euphoric) and cognitive measures, such as memory. Some of the findings from this review, as observed across studies, are summarized as follows: • People experience alcohol's subjective intoxicating effects at lower BAC's than alcoholinduced performance impairment.
• Whereas a linear relationship exists between BAC and performance im pairment over a wide range of BAC's (i.e., the higher the BAC, the stronger the performance impairment), there appears to be a threshold BAC below which people do not experience sub jective intoxication.
• The effects of alcohol are greater on tasks or processes demanding attention or effort (i.e., "controlled" processes) than on tasks or processes making few attentional demands (i.e., "auto matic" processes).
• Seventy to 80 percent of the studies found that BAC's at or below 0.04 percent had significant effects on intoxication ratings and on the per formance of controlled tasks.
• Characteristics of the study subjects, such as expectancy 2 and tolerance, 3 as well as contextual parameters (e.g., time of day or social environment), 1 A BAC of 0.05 percent corresponds to 0.05 gram pure alcohol per 100 milliliters blood.
2 Expectancy means that a person expects certain effects on behavior after the consumption of alcohol; therefore, the person may display the expected behavioral effects whether or not alcohol actually is consumed.
3 Tolerance means that after continued alcohol consump tion, a higher dose than before is required to elicit the same effects. Tolerance can develop between drinking sessions (chronic tolerance) or within one drinking session (acute tolerance). In the latter case, alcohol's effects at a given BAC are higher during the rising phase (i.e., ascending limb) of the BAC curve than at the same BAC during the falling phase (i.e., descending limb) of the BAC curve.
may influence sensitivity to the effects of alcohol.
Rather than consider alcohol's effects only on specific behavioral tasks, some researchers have suggested that acute alco hol administration has a global effect on cognitive functioning. For example, Steele and Josephs (1990) have suggested that alcohol produces a "myopic" effect, allow ing the drinker to focus attention only on the most salient aspects of any given situation and disregarding the significance of other aspects. For example, a person who has been drinking may only focus on and react to the annoying or provocative nature of an acquaintance, rather than considering the implications of reacting in anger.
Although alcoholrelated myopia is unlikely to account for alcohol's effects on behavior in all contexts, other studies support this interpretation. For example, Zeichner and colleagues (1993) examined how much time intoxicated subjects spent reading adjectives that described positive (e.g., bright or polite) or negative (e.g., stubborn or foolish) personality traits of the subjects themselves (i.e., were salient) or of another person (i.e., were nonsalient). Consistent with the myopia hypothesis, subjects spent significantly more time attending to personally salient, negative traits than they did to other types of traits. However, more work is needed to deter mine if this pattern is observed in situa tions more similar to everyday life.

LIMITATIONS OF CURRENT RESEARCH FINDINGS
Although numerous studies have analyzed alcohol's effects on cognitive functioning and performance, their findings may not apply to all members of the population to the same extent. For example, the vast majority of studies include only young, healthy men and thus may not reflect al cohol's effects on older people or women. This bias in the selection of study subjects may be the result of concerns about un detected pregnancy in women or the lack of appropriate control subjects among older people.
Few studies have analyzed gender differences in the consequences of acute alcohol effects on cognitive functioning. Niaura and colleagues (1987) examined the effects of an acute alcohol dose on psychomotor performance, pharmacokinetic response, and cognitive impairment in men and women. This study found a stronger effect on women only in the development of acute tolerance to alcoholinduced memory impairment. Other reports have suggested more wideranging gender differences in the effects of acute alcohol doses (Sutker et al. 1982;Wait et al. 1982). However, current research suggests that when the alcohol dose is adjusted for gender differences in body fat-women generally have a higher proportion of body fat than men-at least some of these differences may be eliminated (Nicholson et al. 1992).
Existing data indicate similar patterns of cognitive dysfunction in male and fe male alcoholics (i.e., after chronic alcohol consumption). This is remarkable because female alcoholics consistently report fewer years of drinking and/or a lesser quantity per drinking occasion than male alcoholics (for reviews, see Glenn 1993; National Institute on Alcohol Abuse and Alcohol ism 1990). Based on these findings, it has been suggested that women have a "tele scoped," or accelerated, progression of the negative consequences of alcohol con sumption (Glenn 1993).

SUMMARY
Numerous diagnostic instruments are available to assess alcoholrelated changes in cognitive functioning and to detect subtle and specific impairment. Based on the performance of specific tasks, neu ropsychological and neurocognitive tests can help identify both the brain structures and the cognitive processes affected by alcohol consumption. These findings may contribute to the development of treatment approaches appropriate for patients with different kinds of cognitive impairment. Furthermore, by revealing information about cognitive impairment, these findings indirectly may stimulate new approaches to the study of the brains of healthy persons. However, to maximize the benefits from these tools, researchers must carefully select the test best suited to answer their specific research question and document how cognitive functioning has been assessed.
The testing instruments have been used in many studies and have provided insight into the consequences of chronic and acute alcohol consumption. However, there are limitations to this work. Foremost is the fact that most of the studies have used primarily healthy young men as subjects. Relatively few studies specifically have assessed the neuropsychological, neu rocognitive, and neurophysiological consequences of alcohol consumption in other population subgroups. Preliminary findings in older people and women under score the necessity of expanding this line of research to understand fully alcohol's effects on cognitive functioning. ■